The intracellular parasite Toxoplasma gondii is a category B priority pathogen that is a major food borne[unreadable] pathogen of humans and livestock, but very little is known about how the parasite is recognized and[unreadable] controlled by the immune system. In Aim 1 we will examine the impact of innate immune signaling pathways[unreadable] on T. gondii infection using fibroblasts, dendritic cells, macrophage and mice containing defined genetic[unreadable] lesions. Particular emphasis will be placed on TRAIL-R and FADD (in collaboration with Project 2) and NK[unreadable] cells and the NK ligand NKG2D (in collaboration with Project 3). In Aim 2 we will identify the major natural[unreadable] antigens recognized by CDS T cells during Toxoplasma infection. We hypothesize that the parasite antigens[unreadable] recognized by CDS T cells will vary depending on the stage of infection and the type of antigen presenting[unreadable] cells involved. In Aim 3, we will examine the impact of innate immune responses and CD4 T cells on the[unreadable] response of CDS T cells. We will quantitate CDS T cell responses to particular antigens in mice lacking CD4[unreadable] T cells or the innate immune pathways identified in Aim 1. We will also use 2-photon imaging to examine the[unreadable] dynamic aspects of immune responses in Aims 1 and 3.